Proposals have hitherto been made for various kinds of polyolefin-based fibers such as fibers comprising a polyolefin alone or conjugate fibers in which the polyolefin is exposed to a part or all of the fiber surfaces. Products such as nonwoven fabrics or woven or knitted fabrics comprising the fibers have widely been utilized in fields for household uses such as makeup puffs, wet tissues or draining bags, medical uses such as base fabrics for fomentations, agricultural and civil engineering uses such as hydroponic mats or draining mats, clothing uses or the like such as underwear.
In these fields of uses, the excellent hydrophilic property is frequently required for the above the products. Because of this, proposals have heretofore been made for methods of applying a hydrophilic treating agent to the polyolefin-based fiber surfaces, for example, a method of applying a treating agent containing a polyoxyalkylene-modified silicone to the fiber surfaces (Japanese Unexamined Patent Publication No. 1-148879), a method of applying a treating agent containing an alkylolamide type compound and a polyoxyalkylene-modified silicone to the fiber surfaces (Japanese Unexamined Patent Publication No. 1-148880) and a method of applying a treating agent containing a polyglycerol ester of a fatty acid to the fiber surfaces (Japanese Unexamined Patent Publication No. 2-216265).
Fibers obtained by the methods or the products comprising said fibers have excellent hydrophilic performances at the beginning. Nevertheless, there are problems in that the hydrophilic performances are easily deteriorated when the fibers or the products are stored for a long period and the deterioration is marked at the time of storing in warehouses or the like where the atmosphere is especially subject to high temperatures and high humidities. Furthermore, there are problems of cases where fiber surface friction is reduced and the carding speed cannot be improved when the above polyoxyalkylene-modified silicone or the polyglycerol-based ester of the fatty acid is applied.
The present invention, therefore, is made in consideration of the problems encountered in the above prior art. An object of the present invention is to provide a hydrophilic fiber hardly deteriorating the hydrophilic performances even when kept in severe atmospheres at high temperatures and high humidities and excellent in stability with lapse of time.